This invention relates in general to transplant trays and in particular to a transplant tray which can be used to provide a germination chamber.
Large scale farming operations for crops such as celery, cauliflower, peppers and tomatoes entail the necessity for transplanting millions of seedlings each year. The seedlings are normally started from seeds in a controlled environment such as that within a greenhouse. Upon reaching a desired size, the seedlings are transplanted for field growth until maturity. Since an extremely large number of seedlings are transplanted and cultivated each year, savings of a fraction of a cent per seed will result in a substantial increase in the profits of the farming operation.
In large scale produce farming, transplant trays are frequently used for seed germination. Typically a transplant tray comprises a number of individual cells. The cells are filled to the top with a growth medium (usually a mixture of soil and peat moss). The center of the growth medium in each cell is then pressed from above to form a depression for receiving a seed. Seeds are then dropped onto the trays so that the center depression in the medium of each cell would receive one seed. The trays are then stacked on to a pallet and the pallet of trays is in turn transported by forklifts, trailers or trucks to a greenhouse. Each tray is then laid out in the greenhouse; in modern greenhouses, it is laid out on T-shaped support beams known as T-rails in the greenhouse, but in older greenhouses, it is simply laid out on benches or on the ground. While in the greenhouse, the seeds germinate and the seedlings grow until they emerge from the growth medium in a few days.
The seedlings are allowed to grow until they reach a desired size and until the growth media in the cells are bound by the roots of the seedlings. The transplant trays are then transported to the field. The seedlings are transplanted in a manner so that the roots of the seedlings and the growth medium bound by the roots remain intact to reduce transplant shock to the seedlings as is well known in the art. After transplanting, the crops are then cultivated until maturity upon which they are harvested.
A transplant tray commonly used in produce farming is in the form of a solid expanded or foamed polystyrene body with holes therein to form the cells, such as that shown in FIG. 1 of U.S. Pat. No. 3,667,159 to Todd. Each cell is generally of squared configuration and tapers downwardly into a small opening at the bottom. A conventional tray such as that proposed by Todd is disadvantageous for a number of reasons. Parts of the foamed polystyrene tray may break off particularly at the edges, so that the cells at the edge of the tray cannot retain as much growth medium as is necessary for the healthy growth of seedlings and may even cause the roots of seedlings to grow outside the cells. When the trays are stacked onto a pallet and the pallet transported by forklifts, trailers or trucks to the greenhouse, the top part of a tray in the stack is in contact with the bottom part of the tray immediately above. When the trays are filled with growth medium, some cells may be over-filled so that the growth medium and the seeds therein are at elevations above the top of the tray. Thus, when another tray is stacked on top of such tray, the growth media and the seeds above the top of the tray may be scraped off by the tray immediately above in the stacking process or in the subsequent transportation. This reduces yield.
When the above-described foamed polystyrene trays are used, the roots of the seedlings frequently grow into the polystyrene material forming the side walls of the cells so that when the seedlings are transplanted, parts of the roots may be broken when the seedlings are pulled from the cell, thereby damaging the seedlings. Furthermore, the polystyrene trays are light so that when empty trays are transported by forklifts or trucks over bumpy roads, the stacks of empty trays are unstable and may fall off the forklift or truck. A strong wind may also scatter the trays. The above-described disadvantages have been remedied to some extent by using improved injection molded plastic trays. When the plastic trays are empty, they can be stacked to improve stability during transport on bumpy roads; they are also heavier so that they are not as likely to be scattered by wind. Such plastic trays are available commercially from several manufacturers. However, the plastic trays are similar to the standard expanded (or foamed) polystyrene trays in that, when such trays are filled with growth media and stacked, the bottom portions of the cells of a tray in the stack are in contact with the growth media contained in the tray immediately below when stacked, so that the growth media and seeds at elevations above the top of the tray below may again be scrapped off. In the case of some types of plastic trays now available, the bottom portions of cells of a tray may actually compress the growth media and seeds in the cells of the tray immediately below. It is therefore desirable to provide trays which do not have such disadvantageous when stacked.
As described above, when the seedlings reach a certain stage of development, the seedlings together with the growth medium are ready to be transplanted to a more permanent location for cultivation until maturity. Crops such as celery are left in the greenhouse typically for 70-80 days before they are transplanted whereas cauliflower is typically left for 30-50 days. During the entire process from germination until maturity, it is desirable to provide conditions which will insure that the crops mature at about the same time. The resulting uniformity at the time of harvest increases the percentage of crops which can be harvested at one time which in turn results in higher yields and/or reduced harvesting cost.
Once the seedlings are transplanted, they are usually in an open field where the soil, water supply, fertilizer and weather conditions are much less controllable than when they are in a greenhouse. Therefore to increase the chances that a batch of crops will mature at the same time, it is important that they germinate and emerge at about the same time while they are still in a controlled environment such as in a greenhouse. For this reason, it is important to provide germination conditions which are uniform for the entire batch of seeds so that they will emerge from the growth media at about the same time. To provide uniform germination conditions, it is desirable for the transplant trays to be laid out in the greenhouse immediately after seeding so that the environment surrounding the trays may be controlled to be uniform. Furthermore, the conditions in the greenhouse may be controlled to optimize germination. With most crops, this means heating the greenhouse which is expensive.
In order to save expensive space in the greenhouse, some growers elect to keep their seeded trays in a stack for several days in an uncontrolled environment, such as in an open field where the stack of trays is covered by tarpaulin. When left in an uncontrolled environment, temperature within the stack of filled trays is seldom consistent and oxygen starvation can occur in the middle of the stack. Uneven temperature and humidity within the stack frequently cause non-uniformity in germination and emergence. Thus, when conventional transplant trays are used, a grower must choose between letting the seeded trays occupy expensive space in a greenhouse or suffer non-uniform germination and emergence. It is therefore desirable to provide transplant trays which enhances the uniformity of germination and emergence when the stack of trays are left in an uncontrolled environment.
Different solutions have been proposed for improving uniformity of growth when the stacks of seeded trays are left in an open area. Thus, the stacks may be placed in storage bins to reduce moisture loss and to increase the uniformity of temperature and humidity uniformity within the stacks. This procedure may require many storage bins and much labor. Thus the limited improvement in moisture retention and growth uniformity using the bins is achieved only at considerable expense. Such solution is therefore not entirely satisfactory.
In U.S. Pat. No. 3,965,614, Kienholz describes an apparatus for sprouting seeds such as bean sprouts. The apparatus comprises a vertical arrangement of alternately stacked base members and dish members. The beans to be sprouted are placed on the dish members which are formed with a foraminous bottom wall and an upturned peripheral side wall. Each dish member is then covered by a base member which has an imperforate top wall with a recessed portion for retaining water. Each dish member rests on the top wall of a similar base member with water in its recessed portion. Thus, the beans to be sprouted in a dish member are kept humid by evaporation from the water retained by the recess in the top wall of the base member immediately underneath the dish member. The downturned side wall of the base member is spaced apart from the upturned side wall of the dish member. Since the radial dimension of the dish member is also less than the radial dimension of the base member, a passageway is formed between the chamber for sprouting seeds and the outside environment to assure ventilation of fresh air around the bean sprouts.
The apparatus proposed by Kienholz described above is apparently not suitable for transplanting. Transplant techniques usually require that the seeds germinate in a growth medium. The roots of the seedlings would grow in the medium so that, when the seedlings together with the growth media are transplanted, the seedlings would suffer much less shock as compared to seedlings whose roots are not surrounded by growth medium. Since Kienholz's dish members are foraminous, they are not suitable for retaining a growth medium. Hence Kienholz's apparatus is not suited for transplanting.
Furthermore, Kienholz did not provide individual compartments for individual seeds, so that the roots and seedlings sprouted will become entangled thus making transplanting cumbersome and frequently impossible. Since the sprouting chambers between the dish and base members are ventilated to the outside environment, water must be provided in the recess of the base members to insure a humid environment for sprouting. The provision of water in a transplanting environment may be difficult and costly. The apparatus proposed by Kienholz therefore appears to be disadvantageous for transplanting purposes.
A transplant apparatus is illustrated for example in Canadian Pat. No. 1,009,843 to Bergeron et al. Bergeron et al. disclose a seedling tray growing apparatus comprising a flat support plate having a number of openings through it to support a number of cells open at both the top and bottom ends, one cell in each of the openings. Each of the cells is filled with a growth medium and seeded. The support plate is supported on a frame with four corner legs. The upper corners of the frame for the support plate are recessed into which the corner legs of another support plate may fit; this allows stacking of support plates. The corner legs are of sufficient length to maintain the bottom of the cells above the supporting surface. This permits air circulation beneath the cells as required for air pruning of roots growing out of the bottom of the cells.
The apparatus disclosed by Bergeron et al. leaves the growth media and the seedlings in the cells exposed to the environment into which the trays are placed. When left in an open field, the growth media in the cells may lose moisture so quickly that germination may not occur unless they are continually watered. Netherlands Pat. No. 7,406,925 discloses a transplant device which shares the same disadvantages as those explained above for Canadian Pat. No. 1,009,843.
In U.S. Pat. No. 3,667,159, Todd discloses a seedling flat formed by a number of cells joined together, with side walls and end walls surrounding the cells illustrated in FIGS. 4 and 5. In the patent, Todd did not explain the function of the side and end walls. However, as will be apparent from FIG. 5, the side and end walls have the same height as the cells so that no clearance is left between trays when stacked. Hence, the temperature and humidity conditions within the stack may be uneven. The, growth media and seeds left on trays at elevations above the tops of the trays may be scraped off. When the trays are filled and stacked, the roots of the seedlings will apparently not be automatically air pruned. Moreover, the seedling flats of FIGS. 4 and 5 of Todd cannot be nested so that a stack of empty flats may be scattered by wind and be unstable in transport over bumpy roads.